This invention relates to wafer carriers, more particularly it relates to front opening wafer containers with doors having wafer restraints.
In the processing of wafers into semiconductors, particularly integrated circuit, numerous steps must be performed and the wafers must often be transported facility to facility and internally within a facility in their immediate processing steps. Wafers must be protected during such transportation and storage and immediate processing steps. Recently, semiconductor wafers have increased in size to being as large as 300 mm in diameter. Moreover, the density of circuits on such wafers has dramatically increased. As a result, such wafers are significantly more expensive and protecting same from contamination and/or breaking is critical.
Various aspects of the inventions herein are particularly suitable for use with wafer containers that are commonly known as FOUPs (front opening unified pod) and FOSBs (front opening shipping boxes). These wafer containers have a container portion with interior wafer supports for holding a stack of horizontal wafers in an axially spaced arrangement in the interior of said container portion. Container portion has a front door that allows insertion and removal of the wafers and a door sealingly engages onto the wafer container to latch and seal thereon. Such boxes are, for example, illustrated in U.S. Pat. Nos. 6,267,245; 6,216,874; 6,206,196; 6,010,008; 5,944,194, all of which are owned by the owner of this application and are hereby incorporated in their entireties by reference herein. A generic prior art carrier is depicted in FIG. 1. The wafer container is shown seated on automatic processing equipment 25, and generally includes a container portion 20 and a door 22. The container portion 20 has an open front 24, a top 23, a pair of sides 28, 29, a back side 32, and a bottom 34. A door frame 36 defines the open front and is configured for receiving the door 22. The container portion may have a robotic handling flange 42. Wafer supports 46 in the interior of the container portion support wafers (not shown) that are aligned in a horizontal orientation in a stacked space array. The door has an outwardly facing side 50 and an inwardly facing side 52 and a periphery 54. The periphery 54 has latch slots 58 on the outwardly facing side. An exterior panel 62, which may be the principal structural panel of the door, covers latch mechanisms (not shown) associated with the keyholes 68 and that have latch members (not shown in this view), which extend out of the latch slots 58. Generally, the elements illustrated in FIG. 1 are common to front opening 300 mm wafer containers. Generally, in these types of carries, no consideration is made to prevention of rotation of the wafers during shipping. Such rotation is desirably avoided.
A wafer container having a container portion with an open front for receiving and removal of wafers further includes a door with a cushion system that utilizes a unique wafer restraint system and structural features to provide maximum protection for the wafers and preventing rotation of said wafers. In a preferred embodiment, a stack of wafers in the container portion with their front edges exposed are engaged by a pair of elastomeric cushions mounted on a front surface of the door. Additionally, deflectable wafer springs extend outwardly from the door for making first and last contact with the wafer edges as the door is seated and removed respectively. The inside face of the door may utilize wafer pockets in association with the system that are integrally molded or formed into the door housing.
A feature and advantage of the invention is that the elastomeric cushions prevent rotation of the wafers in the wafer container by softly gripping, with a very high coefficient of friction, the edges of the wafers.
A further feature and advantage of the invention is that, upon removal of the door from a container portion that is fully loaded, the wafer springs operate to restrain the wafers in place in the container portion as the elastomeric cushions are pulled away from engagement with the wafer edges. This prevents the sticking of the wafers to the elastomeric cushions and eliminates the potentially catastrophic result of the wafers following the door as the door is being removed.
A further feature and advantage of the invention is that the use of the elastomeric cushion minimizes wafer breakage and lowers the door closure force.
A further feature of the wafer carrier is a door that may utilize a dome shaped configuration on the inside surface to provide maximum resistance of the door structure to deformation when the door, specifically the wafer restraint system on the door, is in place and in a restraining position with the stack of wafers. In preferred embodiments, the dome structure is provided on the inside facing panel of the door by providing inward recesses at the four inside corners adjacent to the door periphery and sloping the inside facing panel such that said panel generally towards the wafers near the mid-portions of the peripheral sides and the mid-portion of the peripheral to and bottom of said door.
A further feature of the door is that the front of the door covers have a pair of latch cavities on the outwardly facing side of the door. The latch cavities for receiving two latch mechanisms with latch members that extend out the upper and lower peripheral edge of the door. The latch mechanisms are covered by a pair of door panels that utilize hooks that attach to the peripheral edge of the door and further attach with posts near the vertical midsection. The latch cover at the peripheral side edge and at the vertical midsection of the door provides stiffness and resistance to bending of the door. In a preferred embodiment, the attachment of the door panel at the peripheral edge utilizes hook members on the door panel which extend through slots on the peripheral side. Press fit connectors and aperture combinations are preferably utilized to connect the edge of the latch panel approximate the midportion of the door.
A feature and advantage of the wafer restraint system as disclosed herein is that the system imposes significantly less load on the wafers than alternative wafer restraint systems.
Additional objects, advantages, and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.